Method for treating plastic, leather or rubber substrates

ABSTRACT

There is disclosed a method for treating and protecting a substrate, said method comprising coating the surface of said substrate with a composition comprising a blend of 
     (A) a polydimethylsiloxane polymer having a viscosity at 25° C. of 5 to 100,000 cS; and 
     (B) a polyisobutylene oligomer having a number average molecular weight of 200 to 550. The treatment imparts an aesthetically pleasing appearance to the surfaces of plastic, rubber or leather substrates whereby surface gloss is enhanced, but not excessively, as is the case for a comparable all-silicone treating agent.

This is a divisional of copending application Ser. No. 08/317,946 filedon Oct. 4, 1994.

FIELD OF THE INVENTION

The present invention relates to a method for treating plastic, leatheror rubber substrates. More specifically, the invention relates to amethod for treating the substrates with a composition comprising apolyisobutylene (PIB) oligomer and a polydimethylsiloxane (PDMS) fluid.

BACKGROUND OF THE INVENTION

Synthetic leathers based on poly (vinyl chloride) resins (PVC), andpolymer alloys thereof, are extensively used in the automotive andfurniture markets due to their low cost and durability (resistance toozone, ultraviolet radiation, and burning) relative to natural leathers.Protective treatments have been developed for the purpose of cleaning,preserving, and conditioning the surfaces of these PVC products, as wellas those fabricated from various organic rubbers and natural leathers.Specifically, polydimethylsiloxane oils have been used as treatingagents for plastics and rubbers. Such treatments impart improved gloss,restore the appearance, and protect the surfaces against grease, dirt,water, by radiation, thermal degradation and ozone. Thus, for example,U.S. Pat. No. 3,956,174 to Palcher discloses a process for protecting,preserving and renewing surfaces, such as rubber or polymer surfaces,the process comprising applying an emulsion of a polydimethylsiloxanefluid to the surface, allowing the fluid to penetrate the surface for agiven time and then reiterating the application at least one more time.Preferred treating emulsions according to this patent include a polyolcompound, such as diethylene glycol or glycerin.

Unfortunately, treatment with silicone compositions typically also hasan undesirable side effect. These materials impart a "greasy" feel tothe treated substrate. This greasiness is believed to be due to residualmaterial which does not penetrate the surface and can subsequentlyattract dirt or dust.

Another problem associated with the typical silicone formulations is thehigh gloss imparted to the treated surface. This is especiallyproblematic in current model automobiles and minivans which have largedashboards and windscreens. Excessive gloss of the treated surfaces canresult in hazardous driving conditions due to the associated glare. Thisis especially the case during daylight hours when bright sunlightreflects off the treated dashboard, resulting in visual "washout" ortemporary "blinding" of the driver. Although the glare issue in thesecritical automotive applications has been addressed by making use ofplastic materials having lower gloss or matte finishes, these materialsstill require some aftermarket care in order to protect the originalfinish and restore the appearance of aged components. On the other hand,a slight enhancement of gloss is desired since this provides animmediate visual indication of the applied treatment for the consumer.Thus, a successful treating composition must have a delicate balance ofgloss augmentation.

SUMMARY OF THE INVENTION

The present invention overcomes the above mentioned disadvantages andprovides a treating composition, and method of use therefor, whichimparts an aesthetically pleasing appearance to the surfaces of plastic,rubber or leather substrates. The gloss of the treated substrate isenhanced, but not excessively, as is the case for a comparableall-silicone treating agent. Further, substrates treated with theinstant compositions have a significantly reduced degree of greasinessrelative to those treated with a typical silicone oil. Moreover, thetreatment compositions of the invention provide improved protectionagainst the above mentioned environmental factors, particularly thermaldegradation of a plastic (e.g., due to the loss of plasticizer whichoccurs when an automobile is exposed to direct sunlight).

The present invention, therefore, relates to a blend of

(A) a polydimethylsiloxane polymer having a viscosity at 25° C. of about5 to about 100,000 cS; and

(B) a polyisobutylene oligomer having a number average molecular weightof about 200 to about 550, wherein the weight ratio of saidpolydimethylsiloxane (A) to said polyisobutylene (B) is 99:1 to 30:70.

The invention further relates to a method for treating and protecting asubstrate selected from the group consisting of plastic, leather andorganic (i.e., non-silicone) rubber comprising coating the surface ofsaid substrate with the above blend.

The invention also relates to the treated substrate, prepared accordingto the above method.

DETAILED DESCRIPTION OF THE INVENTION

The polydimethylsiloxane (A) of the invention is a homopolymer orcopolymer having a viscosity at 25° C. which is in the range of about 5to about 100,000 cS (5 to 100,000 mm² /s) wherein up to about 35 molepercent, preferably less than 10 mole percent, of diorganosiloxane unitsmay be copolymerized with the dimethylsiloxane units. When the viscosityis greater than about 100,000 cS the penetration of the silicone fluidsinto the substrate to be protected is poor. When the viscosity is lessthan about 5 cS the degree of protection provided is inadequate becausethis component becomes too volatile. Preferably, the viscosity ofcomponent (A) is about 100 to 1,000 cS at 25° C., most preferably about300 to 400 cS.

The organic groups of the above mentioned diorganopolysiloxane units areindependently selected from alkyl radicals having 1 to 16 carbon atoms,halogenated alkyl radicals having 3 to 6 carbon atoms, aryl radicalssuch as phenyl, aralkyl radicals, cycloaliphatic radicals or alkyleneoxide groups, such as ethylene oxide, propylene oxide or copolymericcombinations thereof.

The nature of the terminal groups on the polydimethylsiloxane component(A) is not critical for the purposes of the present invention and thesemay be inert groups, such as trimethylsiloxy, dimethylphenylsiloxy anddiethylphenylsiloxy. They may also be illustrated by groups such asdimethylvinylsiloxy, dimethylhexenylsiloxy, dimethylhydroxysiloxy,dimethylhydrogensiloxy, dimethylalkoxysiloxy, methyldialkoxysiloxy andtrialkoxysiloxy, wherein the alkoxy groups are preferably methoxy. Mostpreferably, component (A) is a polydimethylsiloxane homopolymer havingtrimethylsiloxy terminal units.

Component (A) is well known in the art and is generally availablecommercially.

Component (B) of the invention is a polyisobutylene oligomer having anumber average molecular weight (MW) of about 200 to about 550,preferably about 300 to about 550, and most preferably from about 320 toabout 450. it has been found that when the molecular weight is greaterthan about 550, the compositions result in a film which is sticky andtacky and this, in turn, leads to excessive dirt pick-up by the treatedsubstrate. Such oligomers are known in the art and many are availablecommercially in a variety of molecular weights and end groupcombinations. The polyisobutylene oligomer may have fully saturated endgroups or it may have at least one terminal group which contain afunctional group such as epoxy, methylpropenyl, halide, alkoxyphenylene,hydroxyl, carboxyl, chlorosilyl, vinyl, succinic anhydride, isocyanato,amino or amido. Preferred PIB oligomer has either two fully saturatedend groups or has one epoxy end group and one saturated end group.Again, the specific polymers and oligomers described above can beprepared by methods known in the art.

In order to prepare the compositions of the present invention, abovedescribed components are thoroughly mixed such that the weight ratio of(A) to (B) is about 99:1 to 30:70. Preferably this ratio is about 90:10to about 40:60 and most preferably about 75:25 to about 50:50. Theseblends are then applied to the aforementioned substrates according tothe method of the present invention, described infra.

The compositions of the invention may be applied in the form of anaqueous emulsion, as a solution in an organic or siloxane-based solventor as a neat blend without further dilution. Application of the neatblend is not preferred since it can result in excessive deposition ofthe composition. It is, however, a viable technique when the viscosityof the composition is relatively low, such as below about 500 cS. Anexcess deposition on the substrate can overcome the benefits of reducedbut acceptable gloss, not to mention the obviously undesirable waste ofmaterial.

Compositions of the invention can also be applied from a solution of thePDMS/PIB blend in a volatile carrier, such as a hydrocarbon having fromabout 6 to 16 carbon atoms in its molecule. The hydrocarbon may be astraight or branched chain compound such as heptane, decane, tetradecaneand hexadecane. However, due to current volatile organic compound (VOC)regulations, this is not a preferred delivery system.

Alternatively, low molecular weight linear polysiloxanes having aviscosity below about 5 cS at 25° C. can be used as a solvent.Illustrative solvents are linear diorganopolysiloxanes having a degreeof polymerization of 2 to about 9. Cyclic diorganopolysiloxanes having aviscosity below about 10 cS at 25° C. are also suitable. Illustrativeare cyclics having a degree of polymerization of 4 to about 6, whereinthe organic groups are independently selected from alkyl radicals having1 to 6 carbon atoms. Specific examples of the above siloxanes includehexamethyldisiloxane, octamethylcyclotetrasiloxane anddecamethylcyclopentasiloxane. Mixtures of these siloxanes may also beemployed.

Preferably, the compositions of the present invention are applied froman aqueous emulsion. In this case, the polydimethylsiloxane andpolyisobutylene fluids are preferably premixed and then emulsified.Alternatively, each fluid can be emulsified independently and theresulting emulsions mixed. These emulsions are prepared with the aid ofat least one non-ionic surfactant, standard mixing and dispersiontechniques being employed. The preferred surfactant is an ethoxylatedtrimethylnonanol. Chemically, this surfactant is trimethylnonylphenylpoly(ethylene oxide). Other suitable non-ionic surfactants may beselected from modified polyethoxylated alcohols, inter alia. Thenon-ionic surfactant can be used in combination with an anionicsurfactant, such as an sodium alkylaryl ether sulfate, sodium alkylarylpolyether sulfonate, or a blend of an alkylaryl polyether alcohol withan organic sulfonate. The emulsions preferably contain about 1 to about60 percent of the combined weights of components (A) and (B), mostpreferably about 20 weight percent, the remainder being water,surfactant and additional minor component, described infra. In thisconnection, commercial silicone aqueous emulsions are available whichcontain up to 50% silicone.

In addition to components (A) and (B), the instant compositions maycontain a variety of additives which are not essential or critical toperformance, but may be advantageous in some applications. Thesematerials include rust inhibitors, dyes, UV absorbers, antifoam agents,antimicrobial agents, and the like. When employed, such additives shouldcomprise no more than about 2 parts by weight for each 100 parts byweight of (A) and (B). When the compositions of the invention are to beapplied from an aqueous emulsion, the additives are preferably soluble,or dispersible, in water.

The method of the present invention comprises coating at least a portionof the surface of a plastic, leather or rubber substrate with the abovedescribed composition comprising components (A) and (B). The method ofcoating (or treating) these substrates may be any of those known in theart. Examples of suitable coating methods include wiping, spraying,pouring, brushing, rolling and dipping. Preferably, the composition issparingly applied to the substrate and distributed over the surfacethereof by rubbing with a cloth or paper towel or rag. Alternatively,the composition may be applied to the towel or rag and then rubbed overthe surface of the substrate. After such an application, any water orsolvent used as a carrier for component (A) and (B) is allowed toevaporate to leave a treated substrate. If desired, this treated surfacemay further be buffed or polished to enhance the appearance of the finalfinish. The plastic substrates which benefit from treatment with theinstant compositions include polymers and copolymers of vinylicmonomers, polyurethanes, acrylics and polyolefins, such as polypropyleneand polypropylene/EPDM alloys, inter alia. A preferred utility of theinstant method is the treatment of plasticized PVC films, polymericalloys based on PVC and PVC-coated fabrics found in automotive andfurniture applications. Examples of rubbers which can be treated withthe instant compositions include butyl, urethane and ethylene-propylenediene monomer terpolymers (EPDM), inter alia. Treatment of rubberautomobile tires is a preferred utility in this regard. Both natural andsynthetic leathers (e.g., polyurethane leather, Naugahyde™) also benefitfrom treatment with the instant compositions.

EXAMPLES

The following examples are presented to further illustrate the methodand compositions of this invention, but are not to be construed aslimiting the invention, which is delineated in the appended claims. Allparts and percentages in the examples are on a weight basis and allmeasurements were obtained at about 25° C., unless indicated to thecontrary.

The following materials were employed in the examples:

PDMS A=trimethylsiloxy-terminated polydimethylsiloxane having aviscosity of about 350 cS (350 mm² /sec).

PIB A=Actipol™ E-6, described as an epoxy-terminated polyisobutylenehaving a number average molecular weight of about 365 and a product ofthe Amoco Chemical Company, Chicago, Ill. This oligomer has one terminalgroup of the structure ##STR1## in which Me denotes a methyl radical,the other terminal group being of the formula --C(CH₃)₃.

PIB B=Polysynlane™, described as a saturated polyisobutylene having anumber average molecular weight of about 320 and having one terminalgroup of the formula ##STR2## the other terminal group being of theformula --C(CH₃)₃. It is a product of Polyesther Corporation,Southhampton, N.Y.

PIB C=Indopol™ L-14, described as a vinyl-terminated polyisobutylenehaving a number average molecular weight of about 320 and a product ofthe Amoco Chemical Company, Chicago, Ill. One terminal group of thisoligomer has the vinyl-like structure (2-methylpropenyl) --HC═C(CH₃)₂,the other terminal group having the formula --C(CH₃)₃.

PIB D=Actipol™ E-16, similar to PIB A but having a molecular weight ofabout 975.

PIB E=Indopol™ H-35, similar to PIB C but having a molecular weight ofabout 660.

EXAMPLE 1

The above described PIB and PDMS fluids were pre-mixed in a disposablebeaker, using a spatula, in the proportions shown in Table 1.Separately, trimethylnonylphenyl poly(ethylene oxide) surfactant(Tergitol™ TMN-6; Union Carbide, Danbury, Conn.) and deionized waterwere pre-mixed in a stainless steel beaker using a Cowels blade withmedium agitation. Proportions of water and surfactant used are alsopresented in Table 1. The mixture of PIB and PDMS was then added to thesurfactant-water mixture under fast agitation and the agitation wascontinued for approximately two minutes. The mixture was run through amicrofluidizer until a constant particle size was achieved (at least 4passes).

                  TABLE 1                                                         ______________________________________                                                 PDMS A    PIB    PIB   Surfactant                                                                            Water                                 Formulation                                                                            (g)       Used   (g)   (g)     (g)                                   ______________________________________                                        Control  40.00     --     --    2.2     157.8                                 1        18.75     A      6.25  1.1     78.9                                  2        20.00     A      20.00 2.2     157.8                                 3        6.25      A      18.75 1.1     78.9                                  4        18.75     B      6.25  1.1     78.9                                  5        55.00     B      55.00 6.0     434.0                                 6        6.25      B      18.75 1.1     78.9                                  7        18.75     C      6.25  1.1     78.9                                  8        20.00     C      20.00 2.2     157.8                                 9        6.25      C      18.75 1.1     78.9                                  ______________________________________                                    

All the emulsions had a non-volatile (NV) polymer content between 20%and about 24%.

EXAMPLE 2

The formulations of Example 1 were used to treat two differentautomotive vinyl substrates:

Substrate A=a foam-expanded poly (vinyl chloride) (PVC);

Substrate B=a PVC/ABS alloy, wherein ABS is anacrylonitrile-butadiene-styrene copolymer.

Samples of Substrate A, measuring 2 inches by 31/2 inches, were weighedand each of these was treated with 230 μl of one of the above describedformulations or control. The treatment was applied directly to thesubstrate with a micropipet and the emulsion was wiped in a circularmotion over the entire surface with a 3×3 inch cotton cloth. Thesubstrate was allowed to air dry for 21/2 hours and re-weighed. In thecase of Substrate B, 3×3 inch samples were weighed and treated with 300μl of the formulations or control, in a similar manner.

An objective indication of surface "greasiness" was then obtained bynoting the amount of transfer of applied treatment to a paper tissue, asfollows. One half of a Kimwipe™ tissue was weighed and placed on top ofa treated substrate, whereupon a 100 gram weight having a diameter ofapproximately 1.75 inches (4.5 cm) was placed on top of the tissue andallowed to remain in contact therewith. After 30 minutes, the weight wasremoved and the tissue re-weighed. The weight pick-up and degree ofimprovement over the control was obtained with the aid of the followingequations, the latter measure being presented in Table 2. ##EQU1##

A % Improvement Relative to Control of greater than 25% was deemedsignificant since this is consderably greater than experimental error(about 4 to 7%).

                  TABLE 2                                                         ______________________________________                                               Wt of Trmt                                                                              %          Wt of Trmt                                                                            %                                                Substrate A                                                                             Improvement                                                                              Substrate B                                                                           Improvement                               Form.  (g)       Substrate A                                                                              (g)     Substrate B                               ______________________________________                                        Control                                                                              0.0071    --         0.0080  --                                        1      0.0065    66         0.0076  47                                        2      0.0073    79         0.0085  58                                        3      0.0077    89         0.0074  66                                        4A     0.0060    55         0.0091  58                                        4B     0.0078    53         0.0083  58                                        5      0.0066    76         0.0071  61                                        6      0.0083    100        0.0083  66                                        7      0.0075    55         0.0083  53                                        8      0.0068    66         0.0085  66                                        9      0.0084    100        0.0083  66                                        ______________________________________                                    

All of the formulations of the invention imparted a significant %Improvement over the silicone control, this being an indication ofsubstantivity to the respective substrate.

(COMPARATIVE) EXAMPLE 1

The procedure of Example 1 was followed using Formulations 10 through12, as described in Table 3a.

                  TABLE 3a                                                        ______________________________________                                                 PDMS A           PIB   Surfactant                                                                            Water                                 Formulation                                                                            (g)       PIB    (g)   (g)     (g)                                   ______________________________________                                        10       --        D      165.00                                                                              9.0     651.0                                 11       --        E      165.00                                                                              9.0     651.0                                 12       18.75     E       6.25 1.1      98.9                                 ______________________________________                                    

These formulations had a non-volatile polymer content of 20% and wereused to treat Substrate B, as described above. The visual evaluation ofthese samples, summarized in Table 3b, indicated that PIB having amolecular weight greater than about 550 is not suitable for treatingsuch substrates.

                  TABLE 3b                                                        ______________________________________                                        Formulation                                                                             Wt of Treatment                                                                            Observation                                            ______________________________________                                        10        0.0095 g     Sticky, tacky to touch.                                11        0.0090 g     Sticky; streaked appearance.                           12        0.0087       Sticky.                                                ______________________________________                                    

EXAMPLE 3

Substrate A and Substrate B were again treated according to theprocedures of Example 2. In each case, the sample was weighed beforetreatment and again after drying in ambient air. The 85 degree gloss(per ASTM D523) was recorded using a portable micro TRI gloss meter (BYKGardner Inc., Silver Spring, Md.). At least five readings were takenover the surface of the substrate and these averaged. The treatedsubstrates were then heat aged in an oven at 120° C. After three weeksthe treated substrates were allowed to cool to room temperature,re-weighed, and the 85 degree gloss was again measured. Tables 4a and 4bshow the % gloss retention after heat aging for each formulation and thecontrol. Table 5 shows the % improvement of weight change of eachsubstrate after heat aging relative to the control, wherein thefollowing equations have been utilized: ##EQU2##

                  TABLE 4a                                                        ______________________________________                                        (Substrate A)                                                                          Initial   Final              % Gloss                                 Formulation                                                                            Gloss (%) Gloss (%) Wt. of Trmt.                                                                           Retention                               ______________________________________                                        Control  6.7       4.1       0.0081   61                                      1        5.6       3.4       0.0079   61                                      2        4.9       3.6       0.0072   73                                      3        3.8       3.3       0.0075   87                                      4A       4.1       3.1       0.0075   76                                      4B       3.9       2.7       0.0088   69                                      5        3.5       3.0       0.0086   86                                      6        3.6       2.5       0.0084   69                                      7        5.3       3.4       0.0082   64                                      8        4.7       3.2       0.0075   68                                      9        3.5       2.5       0.0079   71                                      Untreated                                                                              2.6       --        --       --                                      (A)                                                                           ______________________________________                                    

                  TABLE 4b                                                        ______________________________________                                        (Substrate B)                                                                          Initial   Final              % Gloss                                 Formulation                                                                            Gloss (%) Gloss (%) Wt. of Trmt.                                                                           Retention                               ______________________________________                                        Control  9.3       6.8       0.0089   73                                      1        9.0       7.4       0.0069   82                                      2        8.6       6.8       0.0074   79                                      3        8.4       6.2       0.0082   74                                      4A       8.2       7.0       0.0072   85                                      4B       7.9       6.3       0.0086   80                                      5        8.3       6.6       0.0070   80                                      6        8.7       5.9       0.0076   68                                      7        9.1       7.5       0.0080   82                                      8        8.6       6.8       0.0076   79                                      9        8.4       5.8       0.0079   69                                      Untreated (B)                                                                          3.3       --        --       --                                      ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                                    % Improvement                                                                              % Improvement                                        Formulation (Substrate A)                                                                              (Substrate B)                                        ______________________________________                                        Control     --           --                                                   1           4 3          41                                                   2           47           27                                                   3           -25          10                                                   4A          48           34                                                   4B          46           29                                                   5           52           28                                                   6           -99          10                                                   7           55           32                                                   8           45           15                                                   9           61            2                                                   ______________________________________                                    

A value of % Improvement in Table 5 of greater than 25% is consideredsignificant and highly desirable with respect to thermal stability ofthe treatment. Thus, for example, preferred formulations wherein theratio of PDMS to PIB was at least 1:1, and preferably 3:1, show suchimproved stability; they are not readily volatilized at elevatedtemperatures and therefore provide better thermal protection than an allsilicone treatment or blends having a PDMS to PIB ratio of less than1:1.

(COMPARATIVE) EXAMPLE 2

The procedure of Example 1 was followed using Formulations 13 and 14, asdescribed in Table 6a.

                  TABLE 6a                                                        ______________________________________                                                 PDMS A           PIB   Surfactant                                                                            Water                                 Formulation                                                                            (g)       PIB    (g)   (g)     (g)                                   ______________________________________                                        13       --        A      165.00                                                                              9.0     651.0                                 14       --        C      165.00                                                                              9.0     651.0                                 ______________________________________                                    

These formulations had a non-volatile content of 20% and were used totreat Substrate B, as described above. The evaluation of these samples,summarized in Table 6b, indicated that these low molecular weight PIBcomponents alone do not produce any change in the glossiness of thesubstrate.

                  TABLE 6b                                                        ______________________________________                                        Formulation Wt of Treatment                                                                            85° Gloss (Initial)                           ______________________________________                                        13          0.0085 g     3.5                                                  14          0.0090 g     3.4                                                  Untreated   --           3.3                                                  ______________________________________                                    

That which is claimed is:
 1. A substrate selected from the groupconsisting of plastic, leather and rubber, said substrate being treatedwith a blend consisting essentially of(A) a polydimethylsiloxane polymerhaving a viscosity at 25° C. of 5 to 100,000 cS; and (B) apolyisobutylene oligomer having a number average molecular weight of 200to 550, wherein the weight ratio of (A) to (B) is about 99:1 to 30:70.2. The treated substrate of claim 1, wherein said substrate is leather.3. The treated substrate of claim 1, wherein said substrate is aplastic.
 4. The treated substrate of claim 1, wherein said substrate isan organic rubber.
 5. The treated substrate of claim 4, wherein saidplastic is selected from the group consisting of a homopolymer of vinylchloride and a copolymer of vinyl chloride.